Medium transporting unit and medium processing apparatus

ABSTRACT

A holding mechanism is operable to hold a top medium from a plurality of plate-shaped media accommodated in a stacker in a stacked manner. A transport arm supports the holding mechanism. When the lift mechanism lifts down the transport arm, one of a first elastic pressing force and a second elastic pressing force greater than the first elastic pressing force is selectively applied from the holding mechanism to an upper surface of the top medium.

Priority is claimed under 35 U.S.C. §119 to Japanese Patent ApplicationNo. 2007-099886 filed Apr. 5, 2007, which is hereby incorporated hereinby reference in its entirety.

BACKGROUND

The present invention relates to a medium transporting unit thattransports a plate-like medium such as a CD or a DVD and a mediumprocessing apparatus having the medium transporting unit.

BACKGROUND ART

In recent years, medium processing apparatuses such as disc dubbingapparatuses that record data on mediums such as plural blank CDs or DVDsand CD/DVD publishers that can produce and publish a medium byperforming a data recording operation and a label printing operationwere used. Such a kind of medium processing apparatus was known whichhas a drive for driving data on a medium, a printer for performing aprinting operation on a label surface of the medium, and a mediumtransporting unit for holding and transporting the medium to the driveor the printer (for example, see Patent Document 1).

Patent Document 1: Japanese Patent Publication No. 2006-202379A

However, blank mediums that have not been subjected to a recordingprocess and the like are stacked in the medium stacker and a slightclearance in the radius direction of the mediums is generated betweenthe mediums received in the stacker and the stacker. Accordingly, sincethe mediums stacked in the stacker are randomly received in the stacker,the center positions of the mediums may slightly differ from the pickupcenter of the mediums with the medium transporting unit. In this case,at the time of holding the inner surface of the center hole of themedium by the use of claws of a holding portion of the mediumtransporting unit, the holding force moves in the circumferentialdirection and thus the medium may not be satisfactorily held with goodbalance, thereby causing the holding failure.

The upper and lower mediums may be adhered to each other in the stackerso as to cause an adhesive force therebetween. In this case, when theholding force runs off in the circumferential direction, it is difficultto satisfactorily lift up only the uppermost medium.

For example, even when the medium transporting unit is provided with apositioning guide having a cone shape directed downward and the guide isinserted into the center hole of the medium, the medium does not slidein horizontal direction and thus it is difficult to position the centerof the medium with respect to the pickup center. Accordingly, at thetime of holding the inner circumferential surface of the center hole ofthe medium, the holding force moves in the circumferential direction sothat the medium is not held satisfactorily with good balance, therebycausing the holding failure.

In this case, the insertion force of the positioning guide can beenhanced by increasing the pressing force of the holding portion on themedium. However, in a tray of a drive in which a single medium isreceived, a great load is applied to the tray which should move withhigh precision due to the pressing force of the holding portion, therebyaffecting the movement precision and damaging a moving mechanism of thetray.

SUMMARY

An object of at least on embodiment of the invention is to provide amedium transporting unit that can satisfactorily position and hold amedium as a holding target with an appropriate force, regardless of areception state of the medium to be held, and a medium processingapparatus having the medium transporting unit.

In order to accomplish the above-mentioned objects, according to anaspect of at least on embodiment of the invention, there is provided amedium transporting unit for transporting a top medium from a pluralityof plate-shaped media accommodated in a stacker in a stacked manner, themedium transporting unit comprising: a holding mechanism operable tohold the top medium; and a transport arm provided with the holdingmechanism; wherein when the holding mechanism holds the top medium, oneof a first pressing force and a second pressing force greater than thefirst pressing force is selectively applied from the holding mechanismto an upper surface of the top medium.

The second pressing force may be applied to the upper surface of the topmedium when a plurality of media is accommodated in the stacker.

The first pressing force is applied to the upper surface of the topmedium when a single medium is accommodated in the stacker.

According to the above-mentioned configuration of the mediumtransporting unit, since the holding mechanism comes in contact with themedium with one of the first pressing force and the second pressingforce greater than the first pressing force at the time of lifting downthe transport arm, it is possible to position the medium with the mediumguide and to hold the medium with the holding mechanism with the properpressing force depending on the reception state of the medium.

For example, when a single medium received in a drive or a tray of aprinter which hardly requires the pressing force for positioning themedium is positioned and held, the holding portion can be pressed withthe relatively small first pressing force. When a large positionaldifference occurs and the uppermost medium of the mediums stacked in thestacker, in which the adjacent mediums are adhered to each other togenerate an adhesive force, is positioned and held, the holdingmechanism can be pressed against the medium with the second pressingforce greater than the first pressing force. Accordingly, in the driveor the tray of the printer, it is possible to hold the medium withoutcausing any problem with an excessive pressing force.

The medium transporting unit may further comprise and a lift mechanismoperable to lift the transport arm up and down. The transport arm mayinclude: a lifted member fixed to the lift mechanism to be lifted up anddown; a first urging member operable to urge the lifted member upwardwith a first urging force so that the holding mechanism applies thefirst pressing force to the top medium; and a second urging memberoperable to urge the lifted member upward with a second urging forcegreater than the first urging force so that the holding mechanismapplies the second pressing force to the top medium; and the secondurging member may apply the second urging force to the lifted memberwhen the lifted member is lifted down by a predetermined distance.

According to this configuration, when the lifted member is lifted downby the predetermined distance against the first urging member, thesecond urging member is operated by the lifted member. Accordingly, itis possible to easily and properly set the urging force of the firsturging member as the first elastic pressing force and to set the urgingforce of the first urging member, the bending force of the transportarm, and the urging force of the second urging member as the secondelastic pressing force.

The transport arm may further include an arm body and a pressing lever,one end of which is swingably supported in the arm body; the firsturging member may include a first tension spring, one end of which isfixed to the arm body and the other end of which is fixed to the liftedmember; the second urging member may include a second tension spring,one end of which is fixed to the arm body and the other end of which isfixed to the other end of the pressing lever; and the pressing lever mayswing against the second urging force of the second tension spring afterthe lifted member comes in contact with the pressing lever and is lifteddown.

According to this configuration, the urging force of the first tensionspring can be used as the first elastic pressing force until the liftedmember comes in contact with the pressing lever. When the lifted membercomes in contact with the pressing lever and thus the pressing leverswings, the urging force of the first tension spring, the bending forceof the transport arm, and the urging force of the second tension springcan be used as the second elastic pressing force.

The lift mechanism may include a timing belt; and the lifted member mayinclude a belt clip fixed to the timing belt.

According to this configuration, the transport arm can be fixed to thelift mechanism with a simple structure.

The holding mechanism may include a contact portion adapted to come incontact with the upper surface of the top medium in the vicinity of acenter hole formed on the top medium.

According to this configuration, a problem with the adhesion between themediums can be easily solved.

The holding mechanism may include a pressing member operable to press aninner peripheral surface of a center hole formed on the top medium.

According to this configuration, the holding mechanism can hold themedium with a simple structure.

The holding mechanism may include a medium guide having a circulartruncated cone shape directed downward and adapted to be inserted into acenter hole formed on the top medium.

According to this configuration, the uppermost medium can slidehorizontally for positioning by the use of the medium guide against theadhesive force between the uppermost medium and the right below mediumand can be held by the use of the holding mechanism.

The first pressing force may be generated by the first urging force ofthe first urging member; and the second pressing force may be generatedby the first urging force of the first urging member and the secondurging force of the second urging member.

According to the other aspect of at least on embodiment of theinvention, there is provided a medium processing apparatus comprising:the above stacker; the medium transporting unit; and a media drivehaving at least one of a function for writing data on the transportedmedium which is transported by the medium transporting unit and afunction for reading data on the transported medium.

According to the medium processing apparatus having the Above-mentionedconfiguration, since it includes the medium transporting unit that cansatisfactorily position and hold the medium, it is possible to provide amedium processing apparatus with high reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail preferred exemplary embodimentsthereof with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view illustrating an appearance of a publisher(medium processing apparatus);

FIG. 2 is a perspective view illustrating the front side of thepublisher with a case removed from the publisher;

FIG. 3 is a perspective view illustrating the rear side of the publisherwith the case removed from the publisher;

FIG. 4 is a perspective view illustrating a recording unit of thepublisher;

FIG. 5 is a perspective view illustrating a medium transporting unit;

FIG. 6 is a perspective view illustrating a part of the mediumtransporting unit;

FIG. 7 is a perspective view illustrating a connection mechanism betweena transport arm and a timing belt;

FIG. 8 is an enlarged perspective view illustrating the connectionmechanism between the transport arm and the timing belt as viewed fromthe bottom;

FIG. 9 is a perspective view illustrating an internal structure of thetransport arm;

FIG. 10 is a plan view illustrating the transport arm having held amedium as viewed from the bottom;

FIG. 11 is a sectional view illustrating a holding portion of thetransport arm;

FIG. 12 is a perspective view illustrating a medium guide disposed inthe holding portion of the transport arm;

FIG. 13 is a plan view illustrating the medium guide disposed in theholding portion of the transport arm;

FIG. 14 is a plan view of an arm base which is intended to explain aholding mechanism;

FIG. 15 is a perspective view illustrating holding claws of the holdingmechanism;

FIG. 16 is an enlarged plan view illustrating the holding claws;

FIG. 17 is a plan view illustrating movements of swinging plates and theholding claws;

FIG. 18 is a plan view illustrating movements of the swinging plates andthe holding claws;

FIG. 19 is a plan view illustrating movements of the swinging plates andthe holding claws;

FIG. 20 is a sectional view illustrating the holding claws;

FIG. 21 is a plan view of an arm base which is intended to explain aseparation mechanism;

FIG. 22 is a front view illustrating the transport arm when the holdingportion is viewed in a section;

FIG. 23 is a perspective view illustrating the separation mechanism;

FIG. 24 is a sectional view illustrating a swinging mechanism disposedin the separation mechanism;

FIG. 25 is a plan view illustrating the swinging mechanism disposed inthe separation mechanism;

FIG. 26 is a plan view schematically illustrating the movement of theseparation mechanism;

FIG. 27 is a plan view schematically illustrating the movement of theseparation mechanism;

FIG. 28 is a graph illustrating a relation between a down stroke of abelt clip of the transport arm and a load acting on a medium; and

FIG. 29 is a flowchart illustrating a process of controlling a drivingmotor for lifting up and down the transport arm.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a medium transporting unit according to an embodiment ofthe invention and a medium processing apparatus having the mediumtransporting unit will be described with reference to the drawings.

In this embodiment, the invention is applied to a medium processingapparatus including a publisher.

As shown in FIG. 1, the publisher 1 is a medium processing apparatus forrecording data on a disc-like medium such as CD or DVD or printing animage on a label surface of the medium and has a case 2 having asubstantially rectangular hexahedral shape. Shutters 3 and 4 which canbe opened and closed slidably in the lateral direction are attached tothe front surface of the case 2. An operation surface 5 having displaylamps, operation buttons, and the like arranged thereon is disposed atthe left-upper end portion of the case 2 and a medium discharge port 6is disposed at the lower end of the case 2.

The right shutter 3 as viewed from the front side is a door which isopened and closed at the time of setting a blank medium MA not used ortaking out the completed medium MB (see FIG. 2).

The left shutter 4 as viewed from the front side is opened and closed atthe time of replacing an ink cartridge 12 of a label printer 11 (seeFIG. 2). By opening the shutter 4, a cartridge mounting section 14 (seeFIG. 2) having plural cartridge holders 13 arranged in the verticaldirection is exposed.

As shown in FIG. 2, in the case 2 of the medium processing apparatus 1,a blank medium stacker 21 as a medium storage unit in which plural blankmediums MA not yet used and not yet subjected to a data recordingprocess can be stacked and a completed medium stacker 22 as a mediumstorage unit in which completed mediums MB are disposed vertically sothat the center lines of the stored mediums are aligned with each other.The blank medium stacker 21 and the completed medium stacker 22 can beattached to and detached from predetermined positions shown in FIG. 2.

The blank medium stacker 21 has a pair of arc-shaped frames 24 and 25.Accordingly, the blank mediums MA can be received from the top and canbe stacked coaxially in the stacker. The operation of receiving orreplenishing the blank mediums MA in the blank medium stacker 21 can besimply performed by opening the shutter 3 and taking out the stacker.

The completed medium stacker 22 has the same structure and includes apair of arc-shaped frames 27 and 28. Accordingly, the completed mediumsMB can be received from the top and can be stacked coaxially in thestacker.

The completed mediums MB (that is, mediums having been completelysubjected to a data recording process and a label-surface printingprocess) may be taken out through the shutter 3.

A medium transporting unit 31 is disposed in the back of the blankmedium stacker 21 and the completed medium stacker 22. In the mediumtransporting unit 31, a chassis 32 is swingably attached to a verticalguide shaft 35 vertically suspended between a base 72 and the top plateof the case 2 (see FIG. 5). A fan-shaped final-stage gear 109 is fixedto a horizontal supporting plate 34 of the chassis 32 (see FIG. 5). Thetransport arm 36 is supported by the chassis 32 so as to freely go upand down. The transport arm 36 can be lifted up and down along thevertical guide shaft 35 by a driving motor 37 which can be a step motorand can horizontally swing about the vertical guide shaft 35. A mediumtransported to the medium discharge port 6 by the medium transportingunit 31 can be taken out of the medium discharge port 6.

Two medium drives 41 vertically stacked are disposed on a side of theupper and lower stackers 21 and 22 and the medium transporting unit 31.A carriage 62 (see FIG. 4) of a label printer 11 is movably disposedbelow the medium drives 41.

The medium drives 41 have medium trays 41 a that can move between a datarecording position where data is recorded on a medium and a mediumtransferring position where the medium is transferred, respectively.

The label printer 11 has a medium tray 51 that can move between aprinting position where an image is printed on a label surface of themedium and a medium transferring position where the medium istransferred (see FIG. 3).

In FIGS. 2 and 3, a state where the medium tray 41 a of the upper mediumdrive 41 is drawn forward and located at the medium transferringposition and a state where the medium tray 51 of the lower label printer11 is located at the label printing position are shown. The labelprinter 11 is an ink jet printer and employs ink cartridges 12 ofvarious colors (6 colors of black, cyan, magenta, yellow, light cyan,and light magenta in this embodiment) as the ink supply mechanism 71.The ink cartridges 12 are mounted on the cartridge holders 13 of thecartridge mounting section 14 from the front side.

Here, a gap through which the transport arm 36 of the mediumtransporting unit 31 can be lifted up and down is formed between thepair of frames 24 and 25 of the blank medium stacker 21 and between thepair of frames 27 and 28 of the completed mediums stacker 22. Aclearance allowing the transport arm 36 of the medium transporting unit31 to horizontally swing and to be located just above the completedmedium stacker 22 is opened between the blank medium stacker 21 and thecompleted medium stacker 22. When the medium tray 41 a is pushed intothe medium drive 41, the transport arm 36 of the medium transportingunit 31 can be lifted down to access the medium tray 51 located at themedium transfer position. Accordingly, it is possible to transport themediums to the individual elements by combination of the liftingoperation and the swinging operation of the transport arm 36.

A waste stacker 52 for storing waste mediums MD is disposed below themedium transfer position of the medium tray 51. For example, about 30waste mediums MD can be stored in the waste stacker 52. In a state wherethe medium tray 51 retreats from the medium transfer position above thewaste stacker 52 to the data recording position, the waste mediums MDcan be supplied to the waste stacker 52 by the use of the transport arm36 of the medium transporting unit 31.

Due to the above-mentioned configuration, the transport arm 36 of themedium transporting unit 31 can transport a medium such as a CD or DVDamong the blank medium stacker 21, the completed medium stacker 22, thewaste stacker 52, the medium tray 41 a of the medium drive 41, and themedium tray 51 of the label printer 11.

As shown in FIG. 4, the label printer 11 includes a carriage 62 havingan ink jet head 61 with ink ejecting nozzles (not shown). The carriage62 horizontally reciprocates along a carriage guide shaft 63 by means ofthe driving force of a carriage motor 65 (see FIG. 3).

The label printer 11 includes an ink supply mechanism 71 having acartridge mounting section 14 to be mounted with ink cartridges 12 (seeFIG. 2). The ink supply mechanism 71 has a vertical structure and isformed upright in the vertical direction on a base 72 of the publisher1. An end of a flexible ink supply tube 73 is connected to the inksupply mechanism 71 and the other end of the ink supply tube 73 isconnected to the carriage 62 (see FIG. 4).

The ink of the ink cartridges 12 mounted on the ink supply mechanism 71is supplied to the carriage 62 through the ink supply tube 73, issupplied to the ink jet head 61 through a damper unit and a pressuredistribution control unit (not shown) disposed in the carriage 62, andthen is ejected from the ink nozzles (not shown).

A pressurizing mechanism 74 is disposed in the ink supply mechanism 71so as to put the main portion is above the ink supply mechanism Thepressurizing mechanism 74 pressurizes the ink cartridges 12 by blowingout compressed air, thereby sending out the ink stored in ink packs ofthe ink cartridges 12.

A head maintenance mechanism 81 is disposed below the home position(position shown in FIG. 4) of the carriage 62.

The head maintenance mechanism 81 includes a head cap 82 covering theink nozzles of the ink jet head 61 exposed from the bottom surface ofthe carriage 62 located at the home position and a waste ink suctionpump 83 sucking the ink discharged to the head cap 82 due to a headcleaning operation or an ink filling operation of the ink jet head 61.

The ink sucked by the waste ink suction pump 83 of the head maintenancemechanism 81 is sent to a waste ink tank 85 through a tube 84.

In the waste ink tank 85, an absorbing material is disposed in a case 86and the top surface is covered with a cover 88 having plural ventholes87.

A waste ink receiver 89 as a part of the waste ink tank 85 is disposedbelow the head maintenance mechanism 81 and receives the ink from thehead maintenance mechanism 81. Then, the ink is absorbed by theabsorbing material.

As shown in FIG. 5, in the medium transporting unit 31, the horizontalsupporting plate 34 and the top plate 33 of the cassis 32 is supportedby the vertical guide shaft 35 disposed in the vertical direction. Here,the chassis 32 is swingable. The transport arm 36 is supported by thechassis 32 so as to be lifted up and down.

As shown in FIG. 6, the lift mechanism of the transport arm 36 includesa lifting driving motor (lift mechanism) 37 as a driving source, whichemploys a pulse motor in this embodiment. The rotation of the drivingmotor 37 is transmitted to a driving pulley 101 through a pinion 97 anda transmission gear 98 fitted to an output shaft of the driving motor37. The driving pulley 101 is supported to be rotatable about ahorizontal rotation shaft in the vicinity of the top end of the chassis32. A driven pulley 103 is supported to be rotatable about thehorizontal rotation shaft in the vicinity of the bottom end of thechassis 32. A timing belt (lift mechanism) 104 is suspended on thedriving pulley 101 and the driven pulley 103. As shown in FIG. 7, a base110 of the transport arm 36 is connected to one horizontal end of thetiming belt 104 through a belt clip (lift member) 112.

Accordingly, when the driving motor 37 is activated, the timing belt 104moves in the vertical direction and the transport arm 36 attachedthereto is thus lifted up and down along the vertical guide shaft 35. Asensor not shown for detecting the home position of the timing belt 104is attached to the chassis 32.

As shown in FIG. 5, a rotation mechanism of the transport arm 36includes a rotational driving motor 105 as a driving source and a pinion(not shown) is fitted to the output shaft of the driving motor 105. Therotation of the pinion is transmitted to the fan-shaped final-stage gear109 through a reduction gear train having a transmission gear 107. Thefan-shaped final-stage gear 109 can rotate horizontally about thevertical guide shaft 35. The final-stage gear 109 is mounted to thechassis 32 having constituent elements of the lift mechanism for thetransport arm 36. When the driving motor 105 is activated, thefan-shaped final-stage gear 109 rotates horizontally and thus thechassis 32 mounted thereon monolithically rotates horizontally about thevertical guide shaft 35. As a result, the transport arm 36 retained bythe lift mechanism mounted on the chassis 32 rotates horizontally aboutthe vertical guide shaft 35. A sensor not shown for detecting the homeposition (a position just above the medium trays 41 a and 51 where thetransport arm 36 is located at the medium transfer position) of thefinal-stage gear 109 and positions just above the blank medium stacker21 and the completed medium stacker 22 is fitted to the base 72.

Next, a supporting structure of the transport arm 36 will be described.As shown in FIGS. 7 and 8, a sliding shaft (support portion) 111 isvertically disposed on the base 110 of the transport arm 36. The slidingshaft 111 is inserted through a shaft hole 112 a of the belt clip 112fixed by holding the timing belt 104 (see FIG. 7) so as to be slidablefrom the upside. In FIG. 8, the timing belt 104 is omitted.

A locking piece 112 b is formed in the belt clip 112. An end of a firsttension spring (first elastic urging means 113) which is a coil springis connected to the locking piece 112 b. The other end of the firsttension spring 113 is connected to a fixed piece 115 formed in the base110 of the transport arm 36 and disposed above the locking piece 112 b.Accordingly, the base 110 of the transport arm 36 is urged downward bythe first tension spring 113.

A fixing portion 112 c for fixing the timing belt 104 therebetween isformed in the belt clip 112.

A pressing lever 116 attached to the base 110 of the transport arm 36 isdisposed below the belt clip 112. The pressing lever 116 is laterallyinserted through an insertion hole 118 formed in a supporting plate 117disposed on the bottom of the base 110 of the transport arm 36 and isswingable about a supporting point in the supporting plate 117. An endof a second tension spring (second elastic urging means) 119 formed of acoil spring having an urging force greater than that of the firsttension spring 113 is connected to an end of the pressing lever 116 andthe other end of the second tension spring 119 is connected to a fixedpiece 120 that is formed in the base and disposed above the end of thepressing lever 116. Accordingly, the end of the pressing lever 116 isurged upward by the second tension spring 119. A swing regulating piece121 formed on the base 110 is disposed above the vicinity of the end ofthe pressing lever 116 and the swing of the pressing lever 116 urgedupward by the second tension spring 119 is regulated to a predeterminedposition. The belt clip 112 is disposed at a position apart from thepressing lever 116 regulated by the swing regulating piece 121, byclearance S.

In the above-mentioned supporting structure, when the timing belt 104 isdriven by the lifting driving motor 37 (see FIG. 5), the transport arm36 is lifted up and down monolithically with the belt clip 112 fixed tothe timing belt 104. When a medium guide 133 to be described later or aholding mechanism 130 comes in contact with the medium and a down loadof the transport arm 36 increases, only the belt clip 112 moves downagainst the urging force of the first tension spring 113 relative to thetransport arm 36. When the belt clip 112 further moves down by means ofthe timing belt 104, the belt clip 112 comes in contact with thepressing lever 116, the transport arm 36 is slightly bent, and then thepressing lever 116 swings about a support point in the supporting plate117 against the urging force of the second tension spring 119.

Next, inner mechanisms of the transport arm 36 will be described.

As shown in FIG. 9, the transport arm 36 includes a longitudinal armbase 125 a having a rectangular shape in the plan view and an arm case125 b having the same profile as the arm base 125 a so as to cover thearm base. The arm base 125 a is provided with a holding mechanism 130for holding a medium M, a separation mechanism 131, and a mediumdetecting mechanism 200. The holding mechanism 130, the separationmechanism 131, and the medium detecting mechanism 200 are covered withthe arm case 125 b.

As shown in FIGS. 10 and 11, a bottom portion in the vicinity of the endof the arm base 125 a serves as the holding portion 132 for holding amedium M. The medium guide 133 is disposed in the holding portion 132.

As shown in FIGS. 12 and 13, the center of the medium guide 133corresponds to the pickup center of the medium M and the medium guidehas a guide portion 135 protruding downward at the center of a fixedportion 134 fixed to the bottom surface of the arm base 125 a. The guideportion 135 has a cylindrical base end 135 a formed with a diameterslightly smaller than that of the center hole Ma of the medium M and aguide surface 135 b formed in a cone shape that points downward from thebase end 135 a. The medium guide 133 is inserted into the center hole Maof the medium M by approaching the medium M, the inner circumferentialsurface Mb of the center hole Ma of the medium m is guided by the guidesurface 135 b, the center position of the medium M is aligned with thecenter position of the medium guide 133 by the guide surface 135 b, andthen the center hole Ma of the medium M is guided by the base end 135 a,whereby the base end 135 a is inserted through the center hole of themedium M.

Three window portions 133 a are formed in the medium guide 133. Threeholding claws 141 to 143 of the holding mechanism 130 and an operationpiece 183 of the pressing lever 182 of the separation mechanism 131 canprotrude and retreat into and from the window portions 133 a.

As shown in FIGS. 12 and 13, the holding mechanism 130 has threecylindrical holding claws 141 to 143 which are disposed at anapproximate equiangular interval (120°) on the same circle. The holdingclaws 141 to 143 protrudes vertically downward from circular hole 125 cformed in the arm base 125 a and are disposed inside the window portions133 a of the medium guide 133. The three holding claws 141 to 143 areinserted into the center hole Ma of the medium, guided to the base end135 a of the medium guide 133, then are made to move outward, and aremade to protrude from the window portions 133 a of the medium guide 133,thereby pressing the inner circumferential surface Mb of the center holeMa of the medium M to hold the medium M.

As shown in FIG. 20, the holding claws 141 to 143 are attached to lowerends of supporting pins 151 to 153 having a diameter greater than theholding claws. The supporting pins 151 to 153 extend upwardly throughthe circular hole 125 c of the arm base 125 a and three swinging plates161 to 163 disposed on the top surface of the arm base 125 a. Swingingcenter axes 171 to 173 are vertically fixed to the arm base 125 a at theequiangular interval on the same circle so as to surround the circularhole 125 c. The swinging plates 161 to 163 are supported to be swingableabout the swinging center axes 171 to 173, respectively.

As shown in FIGS. 14 to 16, each swinging plate 161 to 163 includes afront arm portion 161 a to 163 a extending counterclockwise in the topview, a rear arm portion 161 b to 163 b extending clockwise in the topview, and supporting arms 161 c to 163 c protruding inside the centerhole 125 c from the swinging center, along the arm base 125 a from theswinging center axis 171 to 173. The supporting pins 151 to 153 arevertically formed on the rear surface of the ends of the supporting arms161 c to 163 c, respectively.

A longitudinal hole 161 d in a direction substantially perpendicular tothe circular hole 125 c is formed in the rear arm portion 161 b of theswinging plate 161. A slide pin 163 f protruding downward from the rearend of the front arm portion 163 a of the swinging plate 163 is slidablyinserted through the longitudinal hole 161 d.

A slide surface 163 e (see FIG. 16) in a direction substantiallyperpendicular to the circular hole 125 c is formed at the end of therear arm portion 163 b of the swinging plate 163 and the front end ofthe front arm portion 162 a of the swinging plate 162 is established soas not to come in contact with the slide surface 163 e. A slide surface162 e in the direction substantially perpendicular to the circular hole125 c is formed at the end of the rear arm portion 162 b of the swingingplate 162 and the front end of the front arm portion 161 a of theswinging plate 161 is in sliding contact with the slide surface 162 e.Here, the longitudinal hole 161 d of the swinging plate 161 and theslide surfaces 162 e and 163 e of the swinging plates 162 and 163 areformed in a concave curved shape set to allow the swinging plates 161 to163 to swing the in same direction.

Tension coil springs (urging members) 174 are suspended between the reararm portion 161 b of the swinging plate 161 and the rear arm portion 162b of the swinging plate 162, between the rear arm portion 162 b of theswinging plate 162 and the rear arm portion 163 b of the swinging plate163, and between the rear arm portion 163 b of the swinging plate 163and the rear arm portion 161 b of the swinging plate 161. By means ofthe tension of the tension coil springs 174, the swinging plates 161 to163 are supported without swinging independently and the urging force,in the direction indicated by arrow R1 in FIG. 16, that is, in thedirection in which the holding claws 141 to 143 move outward, is appliedto the swinging plates 161 to 163.

In the state shown in FIG. 16, the circumscribed circle of the holdingclaws 141 to 143 attached to the ends of the supporting arms 161 c to163 c of the swinging arms 161 to 163 has a diameter greater than theinner diameter of the center hole Ma of the medium M. In this state,when swinging plate 161 is made to swing in the direction indicated byarrow R2, the other swinging plates 162 and 163 accordingly swing in thesame direction as indicated by arrow R2. As a result, the supportingarms 161 c to 163 c of the swinging plates 161 to 163 move to the centerof the circular hole 125 c and the holding claws 141 to 143 attached tothe ends move inward so that they can be inserted into the center holeMa of the medium M.

In this state, when the holding claws 141 to 143 are inserted into thecenter hole Ma of the Medium and then the swinging plates 161 to 163 aremade to swing in the opposite direction R1, the holding claws 141 to 143move outward in the radius direction. As a result, the holding claws 141to 143 are pressed on the inner circumferential surface Mb of the centerhole of the medium M, thereby holding the medium M.

As shown in FIG. 14, an operation arm 161 g extending to the oppositeside of the supporting arm 161 c is formed in the swinging plate 161.The end of one arm portion 175 a of a link 175 is rotatably connected tothe end of the operation arm 161 g. The link 175 is supported by the armbase 125 a so as to be rotatable about a middle portion thereof and theend of the opposite arm portion 175 b is connected to an operation rod176 a of an electromagnetic solenoid 176. When the electromagneticsolenoid 176 is turned off, the operation rod 176 a protrudes by actionof the spring force of a built-in spring.

In this state, where the electromagnetic solenoid 176 is turned on, theoperation rod 176 a is reversely inserted against the spring force inthe electromagnetic solenoid, the link 175 swings clockwise, and theswinging plate 161 thus swings in the direction of R2. Then, as shown inFIG. 17, the slide surface 162 e of the rear arm portion 162 b of theswinging plate 162 comes in sliding contact with the end of the frontarm portion 161 a of the swinging plate 161 and the inner surface of thelongitudinal hole 161 d of the rear arm portion 161 b of the swingingplate 161 comes in sliding contact with the slide pin 163 f of the frontarm portion 163 a of the swinging plate 163. Accordingly, the slidesurface 162 e of the swinging plate 162 comes in sliding contact withthe end of the front arm portion 161 a of the swinging plate 161 andslides outward in the diameter direction of the circular hole 125 c,whereby the swinging plate 162 swings in the direction of R2. The innersurface of the longitudinal hole 161 d of the rear arm portion 161 b ofthe swinging plate 161 comes in sliding contact with the slide pin 163 fof the front arm portion 163 a of the swinging plate 163 and thus thefront arm portion 163 a of the swinging plate 163 slides toward thecenter of the circular hole 125 c, whereby the swinging plate. 163 alsoswings in the direction of R2.

In this way, when the swinging plate 161 swings in the direction of R2,the swinging force in the direction of R2 of the swinging plate 161 istransmitted to the other swinging plates 162 and 163 and thus theswinging plates 162 and 163 also swing in the direction of R2, as shownin FIG. 18. The holding claws 141 to 143 disposed in the supporting arms161 c to 163 c of the swinging plates 161 to 163 are disposed in thecircumscribed circle sufficiently smaller than the center hole Ma of themedium M and move inward until it can be inserted into the center holeMa of the medium M.

In this state, when the electromagnetic solenoid 176 is turned off, theoperation rod 176 a is made to protrude by means of the spring force ofthe spring in the electromagnetic solenoid and the tension coil spring174 and the link 175 thus swings. Then, the swinging motion of the link175 is transmitted to the swinging plate 161 and thus the swinging plate161 swings in the direction of R1. Accordingly, in the other swingingplates 162 and 163, the rear arm portions 162 b and 163 b move towardthe center of the circular hole 125 c by means of the tension of thetension coil spring 174 and thus the swinging plates 162 and 163 alsoswing in the direction of R1 like the swinging plate 161. As a result,as shown in FIG. 19, the holding claws 141 to 143 move outward and theholding claws 141 to 143 are pressed on the inner circumferentialsurface Mb of the center hole Ma of the medium M, thereby holding themedium M.

At this time, since the swinging plates 162 and 163 swing in thedirection of R1 by means of the tension of the tension coil spring 174independently of the swinging plate 161, the holding claws 141 to 143move outward in the radius direction independently of each other andthus are pressed on the inner circumferential surface Mb of the centerhole Ma of the medium M.

As shown in FIG. 20, each of three holding claws 141 to 143 includes acylindrical pin 141 a to 143 a protruding form the bottom end of thesupporting pin 151 to 153 and an elastic cylinder 141 b to 143 b made ofrubber to surround the pin 141 a to 143 a concentrically. Here, althoughthe cylindrical pin 142 a and the elastic cylinder 142 b are not shownin FIG. 20, these components are provided with the holding claw 142 in asimilar configuration as the holding claws 141 and 143. In the holdingclaws 141 to 143, the downward protruding length 1 is equal to orsmaller than the thickness t1 of the medium M to be held. It ispreferable that the producing length 1 is equal to or greater than thethickness t2 of the inner circumferential surface Mb of the center holeMa of the medium M and equal to or smaller than the thickness t1 of themedium M including the height of a ring-shaped protrusion Mc.Accordingly, when the mediums M stacked in the thickness direction areheld, the holding claws 141 to 143 hold only the uppermost medium Mwithout coming in contact with the inner circumferential surface Mb ofthe second medium M. The portions of the supporting pins 151 to 153close to the holding claws 141 to 143 are contact surfaces 151 a to 151b with the medium Mm to be held.

As shown in FIGS. 21 to 23, the separation mechanism 131 disposed in thearm base 125 a of the transport arm 36 includes a pressing lever 182that is rotatably supported by a support shaft 181 formed in the armbase 125 a. The pressing lever 182 includes two components of a frontlever portion 182 a on the holding side and a rear lever portion 182 bon the rotation side. In the front lever portion 182 a, a cylindricalbearing portion 184 inserted through the support shaft 181 formed in thearm base 125 a is made to protrude upward and the rear lever portion 182b is swingably supported by the bearing portion 184. The front leverportion 182 a and the rear lever portion 182 b are swingable in apredetermined range by a locking portion 185 which is prevented frombeing separated from the front lever portion 182 a and an opening 186having a width greater than the width of the locking portion 185 andbeing disposed in the rear lever portion 182 b. As shown in FIGS. 23 and26, the front lever portion 182 a and the rear lever portion 182 b areurged in a direction by a buffer spring 187 which is a twist coilspring. Specifically speaking, in the buffer spring 187 attached to theouter circumference of the swinging portion of the rear lever portion182 b, one arm portion 187 a urges a receiving portion 182 d of thefront lever portion 182 a and the other arm portion 187 b urges areceiving portion 182 e of the rear lever portion 182 b so as to beapart from each other. Accordingly, in the pressing lever 182, a greatload is applied to an operation piece 183 to be described later when therear lever portion 182 b allows the front lever portion 182 a to swing,and the buffer spring 187 is bent when the front lever portion 182 acannot swing, thereby preventing the damage of the operation piece 183.The front lever portion 182 a has the operation piece 183 bent from thefront end to the down side and laterally bent in an L shape. Theoperation piece 183 is disposed in the medium guide 133 of the holdingportion 132.

In a state where the holding claws 141 to 143 of the holding portion 132hold the medium M, the operation piece 183 of the pressing lever 182 isdisposed horizontal below the medium M. Specifically, the operationpiece is disposed at a position corresponding to the second medium M ofthe mediums stacked in the thickness direction.

When the pressing lever 182 swings at the connection point 181 in thedirection of R3 in FIG. 21, the operation piece 183 protrudes laterallyfrom the window portion 133 a of the medium guide 133 and comes inpressing contact with the inner circumferential surface Mb of the centerhole Ma of the second medium M just below the uppermost medium M held bythe holding claws 141 to 143. When the pressing lever 182 swings in theopposite direction of R4 in this state, the operation piece 183 isinserted into the medium guide 133.

A swing mechanism 190 for allowing the pressing lever 182 to swing isdisposed in the rear lever portion 182 b of the pressing lever 182. Theswing mechanism 190 includes a complex clutch gear 191, a verticalcomplex transmission gear 192, a horizontal complex transmission gear193, and a lock 194.

As shown in FIG. 5, the lock 194 is vertically supported by the chassis32 constituting the medium transporting unit 31 so as to be parallel tothe vertical guide shaft 35. The lock 194 engages with a pinion 193 b ofthe horizontal complex transmission gear 193 supported by the arm base125 a so as to be rotatable about a horizontal shaft 193 a (see FIG.23). By lifting up and down the transport arm 36, the horizontal complextransmission gear 193, which has the pinion 193 b that engages with thelock 194, rotates.

A screw gear 193 c is disposed in the horizontal complex transmissiongear 193. The screw gear 193 c engages with a screw gear 192 b of thevertical complex transmission gear 192 supported by the arm base 125 aso as to be rotatable about a vertical shaft 192 a. Accordingly, whenthe horizontal complex transmission gear 193 rotates, the rotation ofthe horizontal complex transmission gear 193 having the horizontal shaft193 a is transmitted to the vertical complex transmission gear 192having the vertical shaft 192 a through the screw gears 192 b and 193 cengaging with each other, thereby allowing the vertical complextransmission gear 192 to rotate.

The vertical complex transmission gear 192 includes a horizontal gear192 c. The horizontal gear 192 c engages with a horizontal gear 191 b ofthe complex clutch gear 191 supported by the arm base 125 a so as to berotatable about the vertical shaft 191 a. Accordingly, when the verticalcomplex transmission gear 192 rotates, the rotating force of thevertical complex transmission gear 192 is transmitted to the complexclutch gear 191 through the horizontal gears 191 b and 192 c engagingwith each other, thereby allowing the complex clutch gear 191 to rotate.

As shown in FIGS. 24 and 25, the complex clutch gear 191 includes anintermittent gear 191 c that is rotatable relative to the horizontalgear 191 b. A clutch mechanism 195 is disposed between the horizontalgear 191 b and the intermittent gear 191 c. The horizontal gear 191 bhas a cylinder shaft 191 d through which the shaft 191 a is inserted.The cylinder shaft 191 d is inserted through a cylinder shaft 191 eformed in the intermittent gear 191 c.

As shown in FIG. 25, the intermittent gear 191 c has a gear train 196including plural gears 196 a on a part of the circumferential surface.The gear train 196 can engage with the horizontal gear 192 c of thevertical complex transmission gear 192.

The clutch mechanism 195 disposed in the complex clutch gear 191 has atwist coil spring 197 wound on the cylinder shaft 191 e of theintermittent gear 191 c. When the horizontal gear 191 b is made torotate in the counterclockwise direction of R5 as viewed from the upsidein FIG. 25 by the horizontal gear 192 c of the vertical complextransmission gear 192, the intermittent gear 191 c is made to rotatewith the horizontal gear 191 b by the frictional force generated fromthe twist coil spring 197. Accordingly, the gear train 196 engages withthe horizontal gear 192 c of the vertical complex transmission gear 192and thus the intermittent gear 191 c rotates in the direction of R5along with the horizontal gear 191 b. On the contrary, when thehorizontal gear 191 b is made to rotate in the clockwise direction of R6as viewed from the upside in FIG. 25 by the horizontal gear 192 c of thevertical complex transmission gear 192, the intermittent gear 191 c ismade to rotate along with the horizontal gear 191 b by means of thefrictional force generated from the twist coil spring 197. Accordingly,the gear train 196 engages with the horizontal gear 192 c of thevertical complex transmission gear 192 and thus the intermittent gear191 c rotates in the direction of R6 along with the horizontal gear 191b.

A cam hole 198 is formed in the intermittent gear 191 c. A cam pin 182 cprotruding downward from the vicinity of the rear end of the rear leverportion 182 b of the pressing lever 182 is slidably disposed in the camhole 198. The cam hole 198 has a path changing from the center to theouter circumference in the clockwise direction in the top view.Accordingly, when the intermittent gear 191 c rotates in thecounterclockwise direction of R5 in the top view in the state shown inFIG. 26, the cam pin 182 c in the cam hole 198 is displaced to the outercircumference. Accordingly, as shown in FIG. 27, the pressing lever 182swings in the direction of R3 about a connection point 181 and thus theoperation piece 183 protrudes to the outside of the medium guide 133. Inthis state, when the intermittent gear 191 c rotates in the clockwisedirection of R6 in the top view, the cam pin 182 c in the cam hole 198is displaced to the inner circumference. Accordingly, as shown in FIG.26, the pressing lever 182 swings about the connection point 181 in thedirection of R4 and thus the operation piece 183 is inserted into themedium guide 133.

In the separation mechanism 131 having the above-mentionedconfiguration, when the transport arm 36 starts going up, the complexclutch gear 191 starts rotating in the direction of R5. When thetransport arm 36 further goes up and the complex clutch gear 191 rotatesby a predetermined angle (about 45°) from the state shown in FIG. 26 tothe state shown in FIG. 27, the pressing lever 182 swings in thedirection of R3 (see FIG. 21) and thus the operation piece 183 of thepressing lever 182 separates the second medium M in the meantime. Whenthe transport arm 36 goes down, the complex clutch gear 191 rotates inthe direction of R6. Accordingly, the pressing lever 182 rotates in thedirection of R4 (see FIG. 21) and the operation piece 183 is insertedinto the medium guide 133 as shown in FIG. 26. Even when the transportarm 36 goes down in this state, the gear train 196 runs off from thehorizontal gear 192 c after the intermittent gear 191 c of the complexclutch gear 191 rotates by a predetermined angle (about 45°) in thedirection of R6 (see FIG. 26) by the horizontal gear 192 c of thevertical complex transmission gear 192 and thus the intermittent gearidly rotates relative to the horizontal gear 191 b.

As shown in FIG. 9, the medium detecting mechanism 200 includes adetection lever 201 of which the rear end is swingably supported and thefront end is bent downward to protrude toward the bottom surface of thearm base 125 a and a detector 202 disposed aside the detection lever201. In the medium detecting mechanism 200, when the transport arm 36goes down to bring the top surface of the medium M into contact with thedetection lever 201 and thus the detection lever 201 swings upward toallow the detection lever 201 to depart from the detection area of thedetector 202, the detector 202 is turned on and thus it is possible todetect an approaching state to the medium M from the detection signaloutput from the detector 202.

Next, an operation of picking up a medium M in the medium transportingunit 31 having the above-mentioned configuration will be described.

An example where the uppermost medium M of the mediums M stacked is heldand picked up from the blank medium stacker 21 will be described withreference to the flowchart of controlling the lifting driving motor ofthe transport arm, which is shown in FIG. 29.

First, in a state where the transport arm 36 is located at apredetermined height position just above the blank medium stacker 21,the electromagnetic solenoid 176 of the holding mechanism 130 is turnedon. In this state, the operation rod 176 a of the electromagneticsolenoid 176 is inserted against the built-in spring, this movement istransmitted to the swinging plate 161 through the link 175, and theswinging plate 161 swings in the direction of R2 in FIG. 16.Accordingly, the other swinging plates 162 and 163 swing in the samedirection and the holding claws 141 to 143 attached to the ends of thesupporting arms 161 c to 163 c of three swinging plates 161 to 163 movesclose to each other, whereby it gets pointed so as to be inserted intothe center hole Ma of the medium M.

Thereafter, the lifting driving motor 37 of the transport arm 36 isdriven (ST1) and the belt clip 112 fixed to the timing belt 104 goesdown (ST2), thereby starting the lift-down operation of the transportarm 36. When the transport arm 36 is lifted down and gets close to theuppermost medium M, the medium guide 133 of the holding portion 132 isinserted into the center hole Ma of the medium M. Here, even when thecenter of the medium M in the blank medium stacker 21 runs off from thecenter of the holding portion 132, the inner circumferential surface Mbof the center hole Ma of the medium M comes in contact with the conicalguide surface 135 b, the center position of the medium M is thus alignedwith the center position of the medium guide 133 by the guide surface135 b, the center hole Ma of the medium M is guided to the base end 135a, and thus the base end 135 a is inserted through the center hole Ma ofthe medium M. That is, the center of the medium M to be held ispositioned at the center of the holding portion 132 which is the pickupcenter.

At this time, when the end of the detection lever 201 of the mediumdetecting mechanism 200 mounted on the transport arm 36 comes in contactwith the surface of the medium M, the detection lever 201 swings upwardwith the lift-down of the transport arm 36 and the detection lever 201runs off from the detection area of the detector 202, thereby turning onthe detector 202 (ST3) to detect the access state to the medium M. It isdetermined whether the destination of the transport arm 36 is the blankmedium stacker 21 receiving plural mediums stacked therein or the mediumtray 51 or the medium tray 41 a receiving a single medium (ST4). Whenthe destination is the medium trays 41 a and 51 of the drive and theprinter, the driving motor is driven separately (ST5) by adding pulse T2to pulse T1 applied to the driving motor 37, the driving motor isstopped (ST7) by lifting down the transport arm 36 by a predetermineddistance, and the holding claws 141 to 143 of the holding mechanism 130mounted on the transport arm 36 are inserted into the center hole Ma ofthe medium M.

The mediums M are stacked in the blank medium stacker 21. Since thestacked mediums M are in close contact with each other, an adhesiveforce may occur between the mediums M.

Accordingly, when the second medium M is adhered to the uppermost mediumM, it is difficult to horizontally position the uppermost medium only bybringing the holding claws 141 to 143 into contact with the innercircumferential surface Mb of the center hole Ma of the medium.

Accordingly, in the medium transporting unit 31, by applying apredetermined pressing force to the uppermost medium M from the top, thepressing force toward the lateral end of the medium M is applied by theguide surface 135 b of the medium guide 133, thereby satisfactorilymoving and positioning the medium M laterally.

A relation between a position of the belt clip 112 of the transport arm36 and a load on the medium M will be described.

FIG. 28 is a graph illustrating a relation between a down stroke of thebelt clip of the transport arm and a load on the medium.

First, in a state where the holding portion of the transport arm 36 isin contact with the uppermost medium M (a state between A and B in FIG.28), when the driving motor 37 continues driving by further applyingpulse T2 (ST5), the belt clip 112 fixed to the timing belt 104 is lifteddown against the urging force of the first tension spring 113 having asmall spring force, the belt clip 112 goes down by a distancecorresponding to the clearance S, and then the belt clip 112 comes incontact with the pressing lever 116 (state B in FIG. 28). Accordingly,until the belt clip 112 comes in contact with the pressing lever 116after the holding portion 132 comes in contact with the uppermostmedium, the first elastic pressing force including the urging force ofthe first tension spring 113 having the small spring force is applied tothe uppermost medium M (state between A and B in FIG. 28).

When the driving motor 37 is further driven, the belt clip 112 furthergoes down. At this time, since the belt clip 112 is in contact with thepressing lever 116, the lift-down force of the belt clip 112 istransmitted to the transport arm 36 to bend the transporting arm 36 andthe bending force is applied as a pressing force to the uppermost mediumM (state between B and C in FIG. 28).

When the driving motor 37 is further driven (ST5), the belt clip 112goes down and stops (ST7 and ST8), and thus the bending force of thetransport arm 36 is greater than the urging force of the second tensionspring 119 having a great spring force (state C in FIG. 28), thepressing lever 116 swings about a supporting point on the supportingplate 117 against the urging force of the second tension spring 119.Accordingly, the second elastic pressing force obtained by adding theurging force of the second tension spring 119 to the urging force of thefirst tension spring 113 and the bending force of the transport arm 36is applied to the uppermost medium M (states between C and E in FIG.28).

In the medium transporting unit 31 having the above-mentioned loadcharacteristic, the driving motor 37 is stopped at a proper position(for example, position of D in FIG. 28) in the state where the pressingforce obtained by adding the urging force of the second tension spring119 to the urging force of the first tension spring 113 and the bendingforce of the transport arm 36 is applied to the medium M (state betweenC and E in FIG. 28).

As a result, among the stacked mediums M in the blank medium stacker 21,a proper load (about 10 N) can be applied to the uppermost medium M.Accordingly, regardless of the adhesion to the second medium M, it ispossible to satisfactorily move laterally and position the medium M bythe use of the guide surface 135 b of the medium guide 133.

Even when the center position of the medium M runs off, it is possibleto satisfactorily insert the medium guide 133 into the center hole Ma ofthe medium and to position the medium, by applying a load.

When the rigidity of the transport arm 36 is enhanced and the springconstant of the second tension spring 119 is increased, it is possibleto obtain a necessary load by reducing the stroke of the belt clip 112for generating the bending force of the transport arm 36 (state betweenB and C in FIG. 28).

When the medium M is lifted up from the medium trays 41 a and 51 of themedium drive 41 and the label printer 11 including only a single mediumM, ST6 is performed as the determination result whether the destinationof the transport arm 36 is the blank medium stacker 21 or the mediumtray 51 of the medium tray 41 a receiving a single medium (ST4) and onlypulse T1 is thus applied to the driving motor 37 (ST6).

In this case, the driving motor is stopped in the region (clearance S inFIG. 7) where the belt clip 112 fixed to the timing belt 104 is lifteddown against the urging force of the first tension spring 113 having asmall spring force. The medium M can be held by the use of the holdingmechanism 130 in the state (state between A and B in FIG. 28) where thefirst elastic pressing force including the urging force of the firsttension spring 113 having a small spring force is applied until the beltclip 112 comes in contact with the pressing lever 116 after the holdingportion of the transport arm 36 comes in contact with the medium M. As aresult, since the load applied on the medium trays 41 a and 51 at thetime of tacking out the medium M can be reduced, it is possible tosuppress the overload due to the load on the medium trays 41 a and 51.

In this way, in a state where the second elastic pressing force isapplied to the uppermost medium M in the blank medium stacker 21, theholding claws 141 to 143 inserted into the center hole Ma of the mediumM are made to move outward and are pressed on the inner circumferentialsurface Mb of the center hole Ma.

Specifically, first, when the electromagnetic solenoid 176 is turned offand the operation rod 176 a thereof is made to protrude by action of thespring force, the swinging plate 161 connected to the operation rod 176a through the link 175 swings in the direction of R1. Accordingly, theother swinging plates 162 and 163 swing in the direction of R1 by meansof the tension of the tension coil spring 174, similarly to the swingingplate 161. As a result, the holding claws 141 to 143 move outward andthe holding claws 141 to 143 are pressed on the inner circumferentialsurface Mb of the center hole of the medium M, thereby holding themedium M.

At this time, since the swinging plates 162 and 163 swing in thedirection of R1 by means of the tension of the tension coil spring 174independently of the swinging plate 161, the holding claws 141 to 143also move outward in the radius direction independently of each otherand are pressed on the inner circumferential surface Mb of the centerhole Ma of the medium M.

Therefore, even when the center position of the uppermost medium M runsoff from the pickup center, the holding claws 141 to 143 move outwardindependently and thus all the holding claws 141 to 143 come in contactwith the inner circumferential surface Mb of the center hole Ma of themedium M, thereby satisfactorily preventing holding failure and thelike.

In addition, the downward protruding length of the holding claws 141 to143 is equal to or less than the thickness of the medium to be held.Accordingly, even when the center position of the second medium M runsoff from that of the uppermost medium M, it is possible to prevent sucha problem that the holding claws 141 to 143 come in contact with theedge of the center hole Ma of the second medium M to cause the holdingfailure.

When the medium M is held in this way, the held medium M is lifted up bylifting up the transport arm 36 in the state where the holding claws 141to 143 move outward in the diameter direction. At this time, since theheld uppermost medium M is satisfactorily held by all the holding claws141 to 143, it is possible to smoothly pick up the medium without anyholding failure.

When the transport arm 36 moves up to pick up the medium M, the pressinglever 182 of the separation mechanism 131 swings in the direction ofarrow R3 in FIG. 21 about the connection point 181 and thus theoperation piece 183 protrudes to the outside of the medium guide 133.

Therefore, even if the second medium M is lifted up by adhesion to thelifted uppermost medium M, the operation piece 183 of the pressing lever182 comes in contact with the inner circumferential surface Mb of thecenter hole Ma of the second medium M to satisfactorily separate thesecond medium, thereby lifting up only the uppermost medium M.

As described above, in the medium transporting unit 31 according to theembodiment, the holding portion 132 of the transport arm 36 comes incontact with the medium M by selectively applying one of the firstelastic pressing force and the second elastic pressing force greaterthan the first elastic pressing force to the medium M at the time oflifting down the transport arm 36. As a result, it is possible toposition the medium M by the use of the medium guide 133 with a properpressing force depending on the receiving state of the medium M and tothen hold the medium by the use of the holding mechanism 130.

For example, when the pressing force is hardly necessary at the time ofpositioning and the single medium M received in the medium trays 41 aand 51 of the drive 41 and the printer 11 which should be picked up witha small pressing force is positioned and held, the holding portion 132can be pressed with the first elastic pressing force relatively small.When a positional error may be greatly caused and the uppermost medium Mof the stacked mediums M in the medium stacker 21 and 22 which areclosely adhered to the just-below medium M to generate an adhesive forceis positioned and held, the holding portion 132 can be pressed on themedium M with the second elastic pressing force greater than the firstelastic pressing force. Accordingly, it is possible to hold the medium Min the medium trays 41 a and 51 of the drive 41 and the printer 11,without causing any problem with the medium dray 41 a and 51 due to theexcessive pressing force.

Until the belt clip 112 as the lift member that is lifted up and down bythe timing belt 104 comes in contact with the pressing lever 116, theurging force of the first tension spring 113 can be used as the firstelastic pressing force. From the state where the belt clip 112 comes incontact with the pressing lever 116 and the pressing lever 116 swings,the urging force of the first tension spring 113, the bending force ofthe transport arm 36, and the urging force of the second tension spring119 can be easily and properly set as the second elastic pressing force.

By providing the second tension spring 119, it is possible to prevent anexcessive load from being applied to the medium in the state between Cand E in FIG. 28. It is also possible to prevent an excessive load frombeing applied to the driving motor 37 and thus to employ a cheapermotor.

Since the contact surfaces 151 a to 153 a of the supporting pins 151 to153 can urge using the stronger urging force of the second tensionspring 119, it is possible to improve the satisfactory holding by meansof the satisfactory contact with the medium M.

In the medium stackers 21 and 22, the uppermost medium M can be made tolaterally slide and positioned by the use of the medium guide 133against the adhesive force to the just-below medium M, therebysatisfactorily holding the medium by the use of the holding mechanism130.

Since the publisher 1 has the medium transporting unit 31 which cansatisfactorily position and hold the medium M, it is possible to providea processing apparatus with high reliability.

The invention may be modified in various forms without being limited tothe above-mentioned embodiments. For example, the control of the drivingmotor 37 having a lift function in the medium transporting unit 31 isselected, after the detector 22 is turned on in FIG. 29 to detectwhether the stacker is a single tray. It may be determined that it is atray when the transport arm is located at the home position and that itis the stacker when the transport arm 36 moves to the medium stackers 21and 22. Alternatively, the determination may be performed when themedium to be held is instructed before the transport arm 36 moves.

Although the timing belt has been used as the lift member, a liftingconfiguration using a rotating shaft on which a spiral groove is formedmay be used. Although the holding mechanism has pressed the innercircumferential surface of the medium, a claw shape engaging with therear surface or the edge portion of the rear surface through the centerhole may be used, or the top surface of the medium may be held bysuction.

Although the tension spring has been used to urge the transport arm 36,a compression spring or a twisted coil spring may be used, but thetension spring is advantageous for management and assembly.

1-11. (canceled)
 12. A medium transporting unit for transporting a topmedium from a stacker in a stacked manner, the medium transporting unitcomprising: a holding mechanism operable to hold the top medium; atransport arm provided with the holding mechanism; and a lift mechanismoperable to lift up and down the transport arm, wherein the holdingmechanism is configured to apply a first pressing force to an uppersurface of the top medium after the holding mechanism comes in contactwith the upper surface of the top medium until the holding mechanism islifted down by a predetermined distance, and to apply a second pressingforce greater than the first pressing force to the upper surface of thetop medium when the holding mechanism is lifted down than thepredetermined distance.
 13. The medium transporting unit as set forth inclaim 12, wherein the transport arm includes: a lifted member fixed tothe lift mechanism to be lifted up and down; a first urging memberoperable to urge the lifted member upward with a first urging force; anda second urging member operable to urge the lifted member upward with asecond urging force greater than the first urging force, and wherein thesecond urging member applies the second urging force to the liftedmember when the lifted member is lifted down by a predetermineddistance.
 14. The medium transporting unit as set forth in claim 12,wherein the stacker further comprises a tray, wherein when the holdingmechanism holds a medium placed in the tray, the holding mechanismapplies the first pressing force to the medium, and wherein when theholding mechanism holds a medium stored in the stacker, the holdingmechanism applies the second pressing force to the medium.
 15. Themedium transporting unit as set forth in claim 12, wherein the holdingmechanism includes a medium guide having a circular truncated cone shapedirected downward and adapted to be inserted into a center hole formedon the medium in order to move and position the medium laterally.